Desizing textiles with chlorite



Patented Aug. 19, 1941 2.253.242 DESIZING TEXTILES WITH CHLORITE James Douglas 'MacMahon, Niagara Falls, and Archie Louis Dubean, Lewiston, N. Y., assignors to The Mathieson Alkali Works, Inc., New York, N. Y., a corporation of Virginia No Drawing. Application March 28, 1939, Serial No. 264,586

4 Claims. 'I'his'invention is concerned with textile treatment and contemplates improvements in textile finishing operations, particularly kiering. More specifically, the invention contemplates improvements in the removal of impurities, especially starchy sizes and the like, from newly woven cellulosic fabrics to improve their appearances and render them amenable to bleaching, dyeing,

printing, and other methods of decoration.

Newly woven cellulosic fabrics, such, for example, as cotton greige cloth, contain variousimpurities which impair appearance and interfere in bleaching, dyeing, etc. Greige cloth,

which may be considered as typical of various other unfinished cellulosic fabrics, contains impurities which may be classified as follows:

1) Natural color bodies from the cotton plant, which impair the whiteness of the cloth and render it non-uniform in appearance.

(2) Motes, i. e. small fragments of cottonseed which adhere tenaciously to the fibres and impair both the hand" and appearance of the cloth.

(3) Waxes and pectins naturally occurring in the cotton fibre, and sizes, usually starchy, that are applied to warp threads during weaving. Such impurities tend to make the cloth waterrepellent, and hence interfere in bleaching and dyeing.

Heretofore customary practice in finishing greige cloth with a view to removing the aforementioned impurities is exemplified by the following sequence of operations:

(1) Singeing to improve the smoothness of the cloth.

(2) Malting, and acid treatment or either one alone, or long soaking in warm water to solubilize starch and the like and to facilitate subsequent removal in kiering. Usually this operation involves saturating the cloth with the de-sizing agent, either malt or acid,- and storage in stacks for a considerable time, after which the cloth is washed in water. I

(3) Mercerizing (if practised).

(4) Kiering, which usually involves boiling the cloth at a pressure in excess of atmospheric for several hours until motes, starch, pectins, waxes, etc., have been removed to the desired extent, and the cloth has acquired a relatively uniform like from a fabric can water absorbency so that it may be bleached and I dyed evenly. The kiering liquor is essentially an aqueous caustic soda solution, to which may be added various other alkalie such as trisodium phosphate and soda ash and detergents or wetting-out agents, such as rosin soap, pine-oil soap, sulphonated castor oil, red oil soap, etc. When the impurities are dimcult to remove or the speciflcations require a high degree of removal, it i customary to turn the cloth over during reloading into a second kier and to repeat the kiering operation.

(5) Water wash.,

(6) Brown sour," acid solution.

(7) Water wash.

(8) Chemic treatment, 1. e. bleaching.

'(9) Water wash.

(10) White sour," i. e. treatment with an aqueous acid solution of a reducing agent, such as sulphurous acid, which serves as an anti-chlor and also helps to brighten the cloth.

.The quality of the finished material is largely dependent upon the kiering operation. Uniformity in bleaching cannot be obtained unless the cloth attains a high and uniform absorbency i. e. a treatment in a dilute for aqueous solution, which, in turn, is dependent upon a uniform removal of waxes, pectins, and sizes. An excessive starch content impairs the permanence of white goods and results in a dull lusterless finish when such gOOds are dyed. Nonuniformity of starch content throughout the cloth results in a corresponding lack of uniformity in appearance of both white and dyed pieces. Heretofore, adequate kiering treatment has involved the consumption of much time, heat, and reagents, together with a large capital investment per unit of cloth treated.

As a result of our investigations, we have discovered that the removal of impurities and particularly the removal or starchy sizes and the be accelerated and made more thorough by including in an alkaline treatment solution a relatively small proportion of sodium chlorite. Moreover, the inclusion of sodium chlorite in a kiering solution eliminates the necessity of preliminary dc-sizing" by melting, acid treatment, or water soaking. Hence, our invention makes possible economies both in the kiering operation and the de-sizing operation and permits the production of better cloth in less timeand at a considerably lower cost.

Our invention, therefore, contemplates the improvement in the kiering of finished cellulosic fabrics which comprises subjecting the fabric to the action of an aqueous alkaline solution containing a relatively small proportion of sodium chlorite. The proportion of sodium chlorite to be employed may vary within reasonably wide limits, but, generally speaking, should be in substantial proportions and preferably in excess of about 0.5 lb. of sodium chlorite per 1000 pounds of dry fabric treated, but not to exceed 10 pounds per 1000 pounds of dry fabric. Thus, we have found that 0.5 lb. of sodium chlorite per 1000 lbs. of cloth is suflicient to bring about a reduction in starch content during a single three-hour boiling in a kiering solution equal to that obtainable in four boiling periods of like duration using the same kiering solution except that no sodium chlorite is included in it. As the concentration of sodium chlorite is increased above a certain maximum (depending upon the nature of the cloth treated and the'amount of starch contained therein) there is no substantial increase in the amount of starch removed, but the residual starch content throughout the cloth becomes somewhat more uniform. This is manifested by an improvement in the starch pattern," 1. e. in the uniformity of blue coloration imparted to the cloth by an iodine solution. All other factors remaining the same, there is a tendency toward improving the absorbency of the cloth as the concentration of sodium chlorite is increased.

We have found that under conditions herein described the chlorite causes substantially no loss in tensile strength.

When the impurities are extremly difficult to remove, or the degree of impurity removal required is particularly high, the cloth may, in accordancewith our invention, be subjected to a second kiering treatment. However, it is not necessary, as in heretofore customary practice, to remove the cloth from the kier to facilitate washing, nor is it necessary to turn the cloth over prior to the second boil. In a two-stage kiering operation employing sodium chlorite in accordance with our invention good results are obtained by draining off the first kiering solution, washing the cloth in the kier, adding a new kiering solution to the kier and thereafter resuming the kiering or boiling operation. In

such a two-stage kiering operation. we have found it advantageous to employ sodium chlorite in either the first or the second stage or in both. Generally speaking, the procedure to employ will be that found heretofore to be suitable for aparticular cloth except that de-sizing by malting, acid treatment or water soaking may be eliminated, sodium chlorite being included in the kier solution. However, if desired, prehminary de-sizing treatment by conventional methods may be practiced. In such case, the addition of sodium chlorite to the kiering solution produces a better result than if it had not been used.

Our invention will be more thoroughly understood in the light of the following practical examples:

Example I Unfinished greige broadcloth with an area of a little over 23,000 sq. yds. and a dry weight of 5,500 lbs. was moistened with water and loaded into a kier containing 25,000 lbs. of an aqueous kiering solution containing 200 lbs. of caustic soda, 200 lbs. of sodium silicate, 6 lbs. of a detergent called "Calgon (essentially sodium metaphosphat) and lbs. of sodium chlorite.

Example II In this instance, the fabric treated was cotton greige for light lawns and light print goods, of which from 6 to 9 yards weighs 1 pound. Herechlorite.

toforecustomary practice for this fabric involved singeing followed by a malting treatment, several hours of storage to solubilize the starch washing into the kier, a two-hour boil at atmospheric and a ten-hour-boil at 15 lbs. pressure in an aqueous alkaline solution of caustic soda having a specific gravity of 3 Tw.

In accordance with the invention, the practice was'changed and 6,000 lbs. of cloth having an area of about 54,000 sq. yds. was singed and (without preliminary de-sizing) washed'through warm water directly into the kier where it was given a two-hour boil at atmospheric pressure followed by a ten-hour boil at 15 lbs. per sq. in. pressure in the same solution as that described above except that it contained 15 lbs. of sodium Following the kiering operation, the cloth was removed from the kier and subjected to further customary finishing treatments, i. e. washed, mercerized, washed, bleached, washed. acid-soured, washed and dried. As it came from the kier the cloth was starch-free and after bleaching and acid-souring, its absorbency was entirely satisfactory, as illustrated by good results obtained in subsequent dyeing operations.

Example III The practice in Example III was similar to that of Example II except that only 10 lbs. of sodium chlorite per 6,000 lbs. of cloth was employed in the kiering operation.

, Emample IV After boiling in the kier for eight hours at 15 lbs. pressure, the cloth was washed in the kier, removed, washed again, subjected to a souring treatment in /2% sulfuric acid, washed once more and bleached.

The resulting product was in all respects as satisfactory as that produced by a malting treatment followed by a second kiering operation for a period of 10 hours for each boil in a solution similar to that described above in all respects, except that it contained no sodium chlorite.

Example V This test was run upon cloth which customarily is de-sized after singeing by being steeped overnight in water and then subjected to a warm water wash before loading into the kier, but all preliminary de-sizing operations were omitted and after singeing the cloth was merely run through rope washers into the kier where it was treated according to the following kier formula:

Pounds Cloth 5,500

3 TW. caustic soda solution, to cover the 010th Pine-oil soap 60 Sodium carbonate 25 Sodium chlorite 15 The kier contents was heated to a temperature ranging from 180 to F. where it was held for two hours. Then the kier was covered and the pressure was raised to lbs. per sq. in. over atmospheric and held for 14 hours. Following this treatment, the kier was cooled and the cloth was taken out, washed with water, bleached, washed, subjected to an acid souring operation with dilute sulphuric acid, washed and dried. The cloth was absorbent, starch-free, and of fair hand as it came from the kier. After bleaching, it was of satisfactory whiteness and of good absorbency.

The inclusion of sodium chlorite in the kiering operation permitted the elimination of the long pre-treatment or de-sizing operation intended to solubilize the starch.

Example VI Pounds Cloth 6000-7000 Tri-sodium phosphate 40 SulfOnated castor oil 30 Sodium silicate 40 Caustic soda, 3 /2 Tw. to cover the goods Thereafter, the high construction cloth is given asecond boil using lbs. of sulphonated castor oil and 5 to 8 lbs. of sodium chlorite in 3 Tw.

in caustic to cover, the duration of the second boil being three hours.

In some cases, 15 lbs. of sodiumchlorite is added to the first kiering charge and the second kiering treatment is eliminated.

We have also found that the use of tetrasodium pyrophosphate together with sodium chlorite in the kiering operation is of advantage in that the two cooperate to increase the brightness and absorbency of the cloth. A suitable kiering solution for the practice of this modification of our invention is alkalyzed in the usual degree but contains 2% lbs. of sodium chlorite per 1000 lbs. of cloth and sufilcient tetrasodium pyrophosphate to give a concentration of 1.25 grams per liter of solution.

Although our invention is of great value in ing, gives to the cloth a softer hand, results in a more permanent white, and facilitates uniform calendering.

We claim:

1. In the kiering of unfinished cellulosic fabrics containing starchy materials, the improvement which comprises removing starchy material from the fabric by subjecting it to the action of a hot aqueous alkaline solution containing a relatively low concentration of sodium chlorite, the amount of sodium chlorite present in the solution being less than 10 lbs. per 1000 lbs. of fabric.

2. In the kiering of unfinished cellulosic fabrics containing starchy materials, the improvement which comprises removing from the fabric starchy material and impurities by subjecting it to the action of a hot aqueous alkaline solution containing a relatively low concentration of sodium chlorite, the proportion of sodium chlorite present in the solution being from 0.5 to 10 lbs. per 1000 lbs. of fabric.

3. In the kiering of unfinished cellulosic fabrics containing starchy materials, the improvement which comprises subjecting the fabric without preliminary desizing treatment to the action of ahot aqueous alkaline solution in which sodium chlorite is present in relatively small concentration to remove the starchy material from the fabric, the amount of sodium chlorite present in the solution being less than 10 lbs. per 1000 lbs. of fabric.

4. In the kiering of unfinished cellulosic fabrics containing starchy materials, the improvement which comprises removing starchy material from the fabric by subjecting it to the action of hot aqueous alkalinesolution having a relatively small concentration of sodium chlorite and a relatively small concentration of tetrasodium pyrophosphate, the sodium chlorite present beingfrom 0.5 to 10 lbs. per 1000 pounds of fabric.

JAMES DOUGLAS MACMAHON. ARCHIE L. DUBEAU. 

